We need to be store, outside of EPiServer, a unique identifier for an EPiServer page. Could we use either PageId or PageGUID? After a page has been set up, could the value of either of these fields change?
I would recommend to use the PageGUID if you want a permanent identifier. The PageID is also unlikely to change, but could when moving pagesbetween environments for example.
Thanks. I'll work with PageGUID. I have found in the past that PageId changing when moving from platform (dev->testing->stage->production) and you comment supports that.